The present invention is directed to a system and method for sensing an occupant characteristic, and particularly for sensing occupant position for use in an occupant protection system.
Vehicle occupant protection systems are generally well known in the art. Occupant protection systems help protect vehicle occupants during vehicle crash events. An occupant protection system typically includes one or more actuatable components, such as an air bag, a seat belt pretensioner, a side curtain, etc. During a crash event, these components are actuatable to provide a cushioning/restraining force to the occupant.
Often these protection system components are selectively actuatable based upon a number of factors that may include, among other things, sensed occupant characteristics and/or crash conditions. An air bag, for instance, may be controlled to be actuated or deployed based upon a determination of whether a crash metric, such as crash acceleration, exceeds a threshold value. Likewise, the air bag may also be controlled depending upon a value of a sensed weight of the occupant and/or a sensed position of the occupant.
An air bag is typically inflated by a source of inflation fluid. The source of inflation fluid is operatively connected to the air bag so that it can fill and thereby deploy the air bag. The inflation fluid often includes a gas that is generated from the combustion of a pyrotechnic material. The pyrotechnic material is typically ignited by an electric squib, which receives an ignition signal from a controller. The controller is often a microprocessor or microcomputer, which is programmed to generate the ignition signal based upon input signals it receives from external sensors. The external sensors sense one or more of the above-mentioned factors. The input signals are therefore representative of one or more of the above-mentioned factors. As such, actuation or deployment of the air bag is based upon one or more of the above-mentioned factors.
In addition to using the above-mentioned factors to control the actuation of the air bag, the controller of an occupant protection system may use one or more of the foregoing factors to control the rate at which the air bag is deployed as well as the degree to which the air bag is inflated. For instance, if more than one inflation fluid source is simultaneously connected to the air bag, the rate at which the air bag is deployed and the degree to which the air bag is inflated are controlled by controlling how and when these multiple Inflation fluid sources are ignited. Partial deployment of the air bag is effected, for instance, where the controller sends an affirmative ignition signal to only one of the squibs, thereby igniting only one of the inflation fluid sources. Alternatively, full and rapid deployment of the air bag is effected when the controller simultaneously sends an affirmative ignition signal to all of the squibs, thereby igniting all of the inflation fluid sources simultaneously.
The rate and degree of air bag inflation is also controlled in many ways other than utilizing multiple inflation fluid sources. For instance, vent valves are also used to control the rate and degree of air bag inflation. Vent valves are operatively connected to one or more inflation fluid sources. When fully opened, a vent valve vents a portion of the inflation gas away from the air bag. Accordingly, when a vent valve is fully opened a fair amount of inflation gas is vented away from the air bag and inflation pressure within the air bag is lessened. Conversely, when the vent valve is not opened or is only opened slightly, very little of the inflation gas is vented away from the air bag and the air bag is deployed at a relatively rapid rate. As with the multiple inflation fluid sources, the operation of vent valves is typically controlled by a controller.
The occupant""s position and weight are used to control the manner in which the air bag is deployed. The occupant""s position affects how and to what extend an air bag should be deployed. For instance, if the occupant is displaced in a direction toward the air bag during a crash event, it may be desirable to only partially inflate the air bag as the occupant""s motion expedites the engagement of the air bag and the occupant. Alternatively, if the occupant is moved completely out of position during a crash event, such that deployment of the air bag would offer little or no protection to the occupant, it may be desirable to not deploy the air bag at all. In such a case, the controller simply does not send an affirmative ignition signal to any of the squibs.
Also, an occupant""s weight may be a factor that affects how and to what extent an air bag should be deployed. For example, a larger occupant may require full deployment to afford the desired protection to the occupant, whereas a smaller occupant may only require partial deployment to restrain the occupant in a desired fashion.
For purposes of designing and evaluating occupant protection systems, industrial standards have been established to model, on a theoretical basis, the population as a whole. These standards define theoretical individuals in terms of overall weight, height, torso length, and various other anatomical characteristics. Based on actual measurements of one of these characteristics, such as weight, other characteristics of a vehicle occupant can be assumed, with a predetermined statistical probability of correctness, from the industrial standards.
In accordance with these standards, deployment commands are often programmed into the controller and/or stored within the memory of an occupant protection system. Therefore, if the occupant""s weight falls within an upper weight range, the occupant may be profiled as an adult passenger. The controller then uses the associated deployment command to fully deploy the air bag. As such, the controller sends command signals to the inflation fluid sources and/or vent valves to effect full deployment of the air bag so that the adult passenger is restrained by the air bag in a desired fashion.
Moreover, depending upon the weight of the occupant and his or her related theoretical anatomical dimensions, the air bag is deployed in a crash condition at a time after the onset of a crash which is derived from, typically, a look-up table. Data stored in the look-up table is derived from historical data and/or empirical testing.
Several arrangements exist to deploy an air bag based upon an occupant""s weight and/or position. For instance, U.S. Pat. No. 5,232,243 discloses an occupant sensing apparatus. The apparatus includes an array of sensors located in the seat that is used to determine the occupant""s position and weight and to control deployment of the occupant protection system via determined position and weight.
Similarly, U.S. Pat. No. 5,732,375 discloses a method of inhibitIng or allowing air bag deployment. The patent discloses an array of pressure sensors on a vehicle seat and a microprocessor that is programmed to sample each sensor. The microprocessor also determines the pattern of pressure distribution by evaluating local groups of sensors.
U.S. Pat. No. 5,821,633 discloses a sensor system for use in a vehicle air bag deployment sensor. The sensor system is embedded in a vehicle seat and comprises six sensors. Once the location of the center of force is known from the sensors, appropriate controls are implemented to determine whether and how an air bag is to be deployed.
U.S. Pat. No. 5,474,327 discloses a vehicle occupant protection system. The protection system includes eight pressure sensors located within a seat cushion. The response of each sensor to occupant pressure is monitored by a microprocessor. The microprocessor calculates total weight and weight distribution.
U.S. Pat. No. 5,739,757 discloses a vehicle passenger weight sensor. A vehicle safety system includes crash detection circuitry and a system for determining the weight of a passenger on the vehicle seat. The air bag may be disabled depending upon the detected weight of the passenger. The weight system includes a forward sensor that measures weight on a forward portion of the seat and a rearward sensor that measures weight on a rearward portion of the seat.
U.S. Pat. No. 5,612,876 discloses a device for detecting seat occupancy in a motor vehicle. The device is especially for inhibiting air bag release when a seat is unoccupied. A seat occupancy sensor includes a front sensing region and a rear sensing region to determine whether the front seat passenger is in a sitting position close to the front seat edge of the seat cushion.
It is desirable to track and update the position of the occupant because the position of the occupant may change during a crash event and/or pre-crash braking situation. Also, the position of the occupant may change rather rapidly because crash events and/or pre-crash braking situations often occur in a relatively short period of time.
In accordance with one aspect, the present invention provides a system for determining a vehicle occupant characteristic. The system includes a plurality of sensors for sensing a parameter and outputting a parameter indicative signal. The sensors are arranged in a plurality of groups, with each sensor of a group sensing a similar parameter value. The system includes determination means for utilizing only a portion of the sensors within each group to make a determination regarding the occupant characteristic.
In accordance with another aspect, the present invention provides a system for determining a vehicle occupant weight-related characteristic. The system includes a plurality of weight sensors. Each weight sensor senses an applied force and outputting a signal indicative of the sensed force. The plurality of sensors are located to sense applied force at a plurality of areas of a vehicle seat. The system includes means for utilizing the force indicative signals from only a portion of the sensors to derive an indication of the occupant weight-related characteristic.
In accordance with another aspect, the present invention provides a system for determining an occupant weight-related characteristic. The system includes a plurality of weight sensors located within a vehicle seat. Each of the sensors senses an applied force and outputs a signal indicative of the sensed force. A controller of the system groups the plurality of sensors into a plurality of sensor sets.
In accordance with yet another aspect, the present invention provides a method for determining a vehicle occupant characteristic. A plurality of sensors that sense a parameter are arranged into a plurality of groups. Each sensor of a group senses a similar parameter value and outputs a parameter indicative signal. Only a portion of the sensors within each group is utilizing to make a determination regarding the occupant characteristic.
In accordance with still another aspect, the present invention provides a method for determining an occupant weight-related characteristic. A plurality of sensors located within a vehicle seat is grouped into a plurality of sensor sets. Each of the sensors senses an occupant characteristic and outputs a signal indicative of the sensed occupant characteristic. The output of an Nth sensor in each set is sampled prior to sampling the output of an Nth+1 sensor in another set.